1. Field of the Invention
The present invention relates to a method of manufacturing a thin-film magnetic head having at least a magnetoresistive element for reading.
2. Description of the Related Art
Performance improvements in thin-film magnetic heads have been sought with an increase in surface recording density of a hard disk drive. A composite thin-film magnetic head has been widely used, which is made of a layered structure including a recording head having an induction magnetic transducer for writing and a reproducing head having a magnetoresistive (MR) element for reading. MR elements include an anisotropic magnetoresistive (AMR) element that utilizes the AMR effect and a giant magnetoresistive (GMR) element that utilizes the GMR effect. A reproducing head using an AMR element is called an AMR head or simply an MR head. A reproducing head using a GMR element is called a GMR head. An AMR head is used as a reproducing head whose surface recording density is more than 1 gigabit per square inch. A GMR head is used as a reproducing head whose surface recording density is more than 3 gigabits per square inch.
Methods for improving the performance of a reproducing head include replacing an AMR film with a GMR film and the like made of a material or a configuration having an excellent magnetoresistive sensitivity, or optimizing the MR height of the MR film. The MR height is the length (height) between the air-bearing-surface-side end of an MR element and the other end. The MR height is controlled by an amount of lapping when the air bearing surface is processed. The air bearing surface is the surface of a thin-film magnetic head that faces a magnetic recording medium and may be called a track surface as well.
Many of reproducing heads have a structure in which the MR element is electrically and magnetically shielded by a magnetic material.
Reference is now made to FIG. 22A to FIG. 29A, FIG. 22B to FIG. 29B, FIG. 31 and FIG. 32 to describe an example of a manufacturing method of a composite thin-film magnetic head as an example of a related-art manufacturing method of a thin-film magnetic head. FIG. 22A to FIG. 29A are cross sections each orthogonal to the air bearing surface of the head. FIG. 22B to FIG. 29B are cross sections each parallel to the air bearing surface of the pole portion of the head.
According to the manufacturing method, as shown in FIGS. 22A and 29B, an insulating layer 102 made of alumina (Al2O3), for example, of about 5 to 10 xcexcm in thickness is deposited on a substrate 101 made of aluminum oxide and titanium carbide (Al2O3xe2x80x94TiC), for example. On the insulating layer 102 a bottom shield layer 103 made of a magnetic material and having a thickness of 2 to 3 xcexcm is formed for a reproducing head.
Next, as shown in FIGS. 23A and 23B, on the bottom shield layer 103, alumina or aluminum nitride, for example, is deposited to a thickness of 50 to 100 nm through sputtering to form a bottom shield gap film 104 as an insulating layer. On the bottom shield gap film 104, an MR film having a thickness of tens of nanometers is formed for making an MR element 105 for reproduction. Next, on the MR film a photoresist pattern 106 is selectively formed where the MR element 105 is to be formed. The photoresist pattern 106 is formed into a shape that easily allows lift-off, such as a shape having a T-shaped cross section. Next, with the photoresist pattern 106 as a mask, the MR film is etched through ion milling, for example, to form the MR element 105. The MR element 105 may be either a GMR element or an AMR element.
Next, as shown in FIGS. 24A and 24B, on the bottom shield gap film 104, a pair of first electrode layers 107 whose thickness is tens of nanometers are formed, using the photoresist pattern 106 as a mask. The first electrode layers 107 are electrically connected to the MR element 105. The first electrode layers 107 may be formed through stacking TiW, CoPt, TiW, and Ta, for example. Next, as shown in FIGS. 25A and 25B, the photoresist pattern 106 is lifted off. Although not shown in FIGS. 25A and 25B, a pair of second electrode layers whose thickness is 50 to 100 nm are formed into a specific pattern. The second electrode layers are electrically connected to the first electrode layers 107. The second electrode layers may be made of copper (Cu), for example. The first electrode layers 107 and the second electrode layers make up an electrode (that may be called a lead as well) electrically connected to the MR element 105.
Next, as shown in FIG. 26A and FIG. 26B, a top shield gap film 108 having a thickness of 50 to 150 nm is formed as an insulating layer on the bottom shield gap film 104 and the MR element 105. The MR element 105 is embedded in the shield gap films 104 and 108. Next, on the top shield gap film 108, a top shield layer-cum-bottom pole (called a top shield layer in the following description) 109 having a thickness of about 3 xcexcm is formed. The top shield layer 109 is made of a magnetic material and used for both a reproducing head and a recording head.
Next, as shown in FIG. 27A and FIG. 27B, on the top shield layer 109, a recording gap layer 110 made of an insulating film such as an alumina film whose thickness is 0.2 to 0.3 xcexcm is formed. On the recording gap layer 110, a photoresist layer 111 for determining the throat height is formed into a specific pattern whose thickness is about 1.0 to 2.0 xcexcm. Next, on the photoresist layer 111, a thin-film coil 112 of a first layer is made for the induction-type recording head. The thickness of the thin-film coil 112 is 3 xcexcm. Next, a photoresist layer 113 is formed into a specific pattern on the photoresist layer 111 and the coil 112. On the photoresist layer 113, a thin-film coil 114 of a second layer is then formed into a thickness of 3 xcexcm. Next, a photoresist layer 115 is formed into a specific pattern on the photoresist layer 113 and the coil 114.
Next, as shown in FIG. 28A and FIG. 28B, the recording gap layer 110 is partially etched in a portion behind the coils 112 and 114 (the right side of FIG. 28A) to form a magnetic path. A top pole 116 having a thickness of about 3 xcexcm is then formed for the recording head on the recording gap layer 110 and the photoresist layers 111, 113 and 115. The top pole 116 is made of a magnetic material such as Permalloy (NiFe) or FeN as a high saturation flux density material. The top pole 116 is in contact with the top shield layer (bottom pole) 109 and is magnetically coupled to the top shield layer 109 in a portion behind the coils 112 and 114.
As shown in FIG. 29A and FIG.29B, the recording gap layer 110 and the top shield layer (bottom pole) 109 are etched through ion milling, using the top pole 116 as a mask. Next, an overcoat layer 117 of alumina, for example, having a thickness of 20 to 30 xcexcm is formed to cover the top pole 116. Finally, machine processing of the slider is performed to form the air bearing surfaces of the recording head and the reproducing head. The thin-film magnetic head is thus completed. As shown in FIG. 29A and FIG. 29B, the structure is called a trim structure wherein the sidewalls of the top pole 116, the recording gap layer 110, and part of the top shield layer (bottom pole) 109 are formed vertically in a self-aligned manner. The trim structure suppresses an increase in the effective track width due to expansion of the magnetic flux generated during writing in a narrow track.
FIG. 30 is a top view wherein the MR element 105, the first electrode layers 107 and the second electrode layers 118 are formed on the bottom shield gap film 104. FIG. 31 is a top view of the thin-film magnetic head manufactured as described above. The overcoat layer 117 is omitted in FIG. 31. FIG. 22A to FIG. 29A are cross sections taken along line 29Axe2x80x9429A of FIG. 31. FIG. 22B to FIG. 29B are cross sections taken along line 29Bxe2x80x9429B of FIG. 31.
As shown in FIG. 30 and FIG. 31, the related-art thin-film magnetic head has the structure wherein the electrode layers 107 and 118 connected to the MR element 105 are inserted in a wide region between the bottom shield layer 103 and the top shield layer 109 for shielding the MR element 105. The very thin bottom shield gap film 104 and top shield gap film 108 are each placed between the shield layer 103 and the electrode layers 107 and 118 and between the shield layer 109 and the electrode layers 107 and 118, respectively. High insulation property is therefore required for the shield gap films 104 and 108. The yield of the thin-film magnetic heads thus greatly depends on the insulation property.
With improvements in performance of the recording head, a problem of thermal asperity comes up. Thermal asperity is a reduction in reproducing characteristic due to self-heating of the reproducing head during reproduction. To overcome thermal asperity, a material with high cooling efficiency is required for the bottom shield layer 103 and the shield gap films 104 and 108 in the related art. Therefore, the bottom shield layer 103 is made of a magnetic material such as Permalloy or Sendust in the related art. The shield gap films 104 and 108 are made of a material such as alumina, through sputtering, into a thickness of 100 to 150 nm, for example. The shield gap films 104 and 108 thus magnetically and electrically isolate the shield layers 103 and 109 from the MR element 105 and the electrode layers 107 and 118.
It is inevitable that thermal asperity should be overcome in order to improve the performance of the reproducing head. Recently, the thickness of the shield gap films 104 and 108 has been reduced to as thin as 50 to 100 nm, for example. The cooling efficiency of the MR element 105 is thereby improved so as to overcome thermal asperity.
However, since the shield gap films 104 and 108 are formed through sputtering, faults may result in the magnetic and electrical insulation that isolates the shield layers 103 and 109 from the MR element 105 and the electrode layers 107 and 118, due to particles or pinholes in the films. Such faults more often result if the shield gap films 104 and 108 are thinner.
In order to improve the output characteristic of the reproducing head, it is preferred that the wiring resistance of the electrode connected to the MR element is as low as possible so that a minute change in the output signal corresponding to a minute change in resistance of the MR element can be detected. Therefore, the areas of the electrode layers 118 are often designed to be large in the related art. However, the areas of the portions of the electrode layers 118 that face the shield gap films 104 and 108 are increased, as a result. If the shield gap films 104 and 108 are thin as described above, magnetic and electrical insulation faults may more often result between the electrode layers 118 and each of the shield layers 103 and 109.
As described above, it is preferred that the wiring resistance of the electrode connected to the MR element is low to improve the output characteristic of the reproducing head. However, there is a limit to reducing the wiring resistance of the electrode since the electrode is made up of the electrode layers 107 and 118 as thin as 50 to 100 nm inserted between the shield layers 103 and 109 in the related-art thin-film magnetic head.
Since a narrow track width is required for the thin-magnetic head, a minute-size MR element is required. For a GMR head, in particular, it is required to precisely detect the output signal of the minute MR element. It is therefore required to reduce noises caused by internal factors such as the coils of the induction-type recording head or external factors such as the motor of the hard disk drive. However, the electrode layers 118 carry noises in the related-art thin-film magnetic head. Such noises may reduce the performance of the reproducing head.
In Japanese Patent Application Laid-open Hei 9-312006 (1997) a technique is disclosed for reducing the electric resistance of the lead and preventing insulation faults between the lead and the top shield. The length of the bottom shield is made shorter than the top shield in the direction of drawing out the lead connected to the MR element from between the top and bottom shields. The thickness of the portion of the lead between the top and bottom shields is made thin. The portion of the lead off the bottom shield is made thick and made to protrude downward.
In the technique, however, the lead is hardly shielded by the bottom shield. As a result, magnetic flux from the coil is easily received in the GMR head that requires a high output. The lead therefore tends to carry noises.
A technique disclosed in Japanese Patent Application Laid-open Hei 10-3617 (1998) is that a conductor connected to an MR element is embedded in a groove formed in an insulating layer between the MR element and a shield layer so as to reduce the shield gap.
However, this technique will not improve the insulation property between the lead and the shield layer.
It is a first object of the invention to provide a method of manufacturing a thin-film magnetic head for improving the insulation property between the shield layer and the electrode connected to the magnetoresistive element without increasing the thickness of the insulating layer between the shield layer and the magnetoresistive element.
It is a second object of the invention to provide a method of manufacturing a thin-film magnetic head for reducing the wiring resistance of the electrode connected to the magnetoresistive element.
It is a third object of the invention to provide a method of manufacturing a thin-film magnetic head for reducing the effect of noises on the magnetoresistive element.
A method of the invention is provided for manufacturing a thin-film magnetic head comprising: a magnetoresistive element; a first shield layer and a second shield layer for shielding the magnetoresistive element, the first shield layer and the second shield layer facing each other with the magnetoresistive element in between; a first insulating layer provided between the magnetoresistive element and the first shield layer and a second insulating layer provided between the magnetoresistive element and the second shield layer; and an electrode connected to the magnetoresistive element. One of the first and second shield layers has a groove in which at least part of the electrode is placed. The at least part of the electrode is insulated and placed in the groove. The method includes the steps of: forming the first shield layer; forming the first insulating layer on the first shield layer; forming the magnetoresistive element on the first insulating layer; forming the second insulating layer on the magnetoresistive element and the first insulating layer; forming the second shield layer on the second insulating layer; and forming the electrode connected to the magnetoresistive element. In the step of forming the electrode and the step of forming one of the shield layers, the electrode and the one of the shield layers are formed by forming the at least part of the electrode, and forming the one of the shield layers to surround the at least part of the electrode, an insulating film being placed between the at least part of the electrode and the one of the shield layers.
According to the method of manufacturing a thin-film magnetic head of the invention, at least part of the electrode is formed, and then one of the shield layers is formed to surround the at least part of the electrode while the insulating film is placed between the at least part of the electrode and the one of the shield layers. The at least part of the electrode is thereby insulated and placed in the groove of the one of the shield layers.
According to the method, the one of the shield layers may be the first shield layer. In the step of forming the electrode and the step of forming the first shield layer, the electrode and the first shield layer may be formed by forming the at least part of the electrode, forming a layer for shielding to be the first shield layer to surround the at least part of the electrode, an insulating film being placed between the at least part of the electrode and the layer for shielding, and flattening the layer for shielding so that the at least part of the electrode is exposed.
According to the method, the one of the shield layers may be the first shield layer. In the step of forming the electrode, the step of forming the first shield layer, and the step of forming the first insulating layer, the electrode, the first shield layer and the first insulating layer may be formed by: fabricating a first electrode portion that forms part of the electrode; fabricating a layer for shielding to be the first shield layer to surround the first electrode portion, an insulating film being placed between the first electrode portion and the layer for shielding; fabricating the first shield layer through flattening the layer for shielding so that the first electrode portion is exposed; fabricating the first insulating layer on the first shield layer; and fabricating a second electrode portion on the first insulating layer, the second electrode portion forming part of the electrode and connecting the first electrode portion to the magnetoresistive element. In this case, the second electrode portion may be formed in a region greater than a region where the first electrode portion is formed.
The method may farther include the step of forming an induction-type magnetic transducer for writing. The transducer includes: two magnetic layers magnetically coupled to each other and including magnetic pole portions opposed to each other, the pole portions being located in regions on a side of a surface facing a recording medium, the magnetic layers each including at least one layer; a gap layer placed between the pole portions of the magnetic layers; and a thin-film coil at least part of which is placed between the magnetic layers, the at least part of the coil being insulated from the magnetic layers.
The method may further include the step of forming an electrode shield layer for shielding the at least part of the electrode. In this case, the method may further include the step of forming an induction-type magnetic transducer for writing. The transducer includes: two magnetic layers magnetically coupled to each other and including magnetic pole portions opposed to each other, the pole portions being located in regions on a side of a surface facing a recording medium, the magnetic layers each including at least one layer; a gap layer placed between the pole portions of the magnetic layers; and a thin-film coil at least part of which is placed between the magnetic layers, the at least part of the coil being insulated from the magnetic layers. In the step of forming the electrode shield layer, the electrode shield layer may be formed at the same time as one of the magnetic layers of the magnetic transducer.
According to the method, at least part of the electrode may be formed through plating. One of the shield layers may be formed through plating.
Other and further objects, features and advantages of the invention will appear more fully from the following description.